I have a DIN-rail mounted Uninterruptible Power Supply (UPS) that has a few digital outputs for status. I’d like to detect a power failure, then shutdown when the UPS indicates that it is running low on power. The question is, should I involve Ignition in this in any way? Or just handle it purely at the OS level? Even if I’m handling it at the OS level, should I send a signal to Ignition that the computer is about to shutdown? (I’m not sure how I would signal Ignition, for that matter.) How do people generally handle a UPS?
If Ignition is running as a service and you shutdown the OS cleanly, Ignition should get shut down cleanly as well.
… I think?
Most of the sites I work at have some kind of power detection in the PLC enclosure. Usually an NC input that opens when pre-UPS power is removed. Then Ignition gives a power failure alarm. I wouldn’t think anything further would be needed.
And as Kevin says as long as the OS is shutdown cleanly Ignition will be shutdown cleanly. There may be the odd situation where the OS halts the service because it didn’t shutdown when the OS told it to, but if that happens there are probably other problems with your Ignition setup / programming you have in it or something.
If you have a PLC with an open digital input, then I would recommend having an alarm as above. Otherwise adding an alarm depends on how hard it will be to add, how likely it is that the users don’t already know there is a problem, and how important it is that the users know about the power problem before Ignition stops running.